Steve,
The car bodies and frame structure of the "F" model locomotives was unusable on GP type locomotives. The "F" carbody was sort of a bridge structure. The frame was not self supporting. The framework of the carbody and the frame was one integral structural assembly. The outside covering was strictly a non structural enclosure. For GP and SD locomotives, on the other hand, the frame was a self supporting stand alone structure. The complete carbody was simply an enclosure with no structural function.
The trade in program that began with the GP20 model, salvaged usable and rebuildable components. The rest was scrapped. Components included truck frames, traction motor frames and armature cores, generator frames and armature cores, engine crankshafts, cams, pumps, gears plus other sundry items. Customers could trade a four axle locomotive for a six axle and still get credit for components such as truck frames which then went into a pool. In some case, EMD even took non EMD locomotives in trade. In most cases, nothing was used from those locomotives, but some GP30s and GP35s were equipped with rebuilt Alco trucks if the customer requested the reuse. The customer still received some credit for the non EMD locomotive. If a trade in piece could not be salvaged, such as a broken crankshaft, the customer did not receive credit for that item and was billed for new. They could ship another qualified crankshaft in if they so desired. As locomotive design evolved, fewer components were reusable and the program gradually faded. The development of the AR10 alternator eliminated the generator trade in from older locomotives. The introduction of the 710 model diesel engine eliminated most of the salvageable engine components.
From EMD's standpoint, it was a complicated book keeping process in the days before computers. For the customer, it proved to be an outstanding opportunity to upgrade their motive power, reduce locomotive fleets and gain significant financial benefit from their old trade in power. The Q was an early and frequent participant in the trade in program up through the 40 series models. GE, of course, offered a similar program, but could reuse most of the components. Government accounting procedure changes in the early stage of the program helped facilitate the process.
Bill Barber Gravois Mills, MO Mon Jan 2, 2012 11:07 pm (PST)
<< It was 5 Q units and 5 GN units. Some of the GN units started out as FT
units from what I've seen. >>
GN FT units were traded in on some of the GP20's. While some components
from the FT's might have been re-manufactured and then ended up in the
GP20's, that's about the extent of it. For one thing, FT and GP's have
different wheelbases and frames . . . .
Steve Haas
Snoqualmie, WA
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